CN114696781A

CN114696781A - Elastic wave device and module

Info

Publication number: CN114696781A
Application number: CN202110667617.9A
Authority: CN
Inventors: 远藤祐喜
Original assignee: Sanyan Japan Technology Co ltd
Current assignee: Sanyan Japan Technology Co ltd
Priority date: 2020-12-30
Filing date: 2021-06-16
Publication date: 2022-07-01
Also published as: JP6940085B1; JP2022104846A

Abstract

An elastic wave device comprising a piezoelectric substrate, and a band pass filter formed on the piezoelectric substrate and including a resonator having a first IDT electrode, a second IDT electrode, a third IDT electrode, a fourth IDT electrode, and a fifth IDT electrode, the number of pairs of the third IDT electrode being greater than the sum of the number of pairs of the first IDT electrode, the number of pairs of the second IDT electrode, the number of pairs of the fourth IDT electrode, and the number of pairs of the fifth IDT electrode, whereby an elastic wave device using a resonator having a more rectangular shape, a low loss, and excellent passband characteristics can be provided, and a module comprising the elastic wave device.

Description

Elastic wave device and module

Technical Field

The present invention relates to an elastic wave device and a module including the elastic wave device.

Background

With the progress of technology in recent years, smart phones and the like representing mobile communication terminals have been remarkably reduced in size and weight. An elastic wave device that can be miniaturized is used for a filter used in the mobile communication terminal. Also, in a mobile communication system, a demand for a communication system capable of simultaneously receiving and transmitting, for example, a duplexer, has sharply increased.

In this case, a resonator having an unbalanced-balanced conversion function, which is used as a filter on the receiving side of the duplexer, is used. In addition, with the change of mobile communication systems, the specification requirements for duplexers have become more and more strict. In other words, a resonator which is more rectangular than the conventional ones, has low loss, and has considerably excellent passband characteristics is necessary.

A technique relating to an elastic wave device is exemplified in patent document 1 (japanese patent laid-open No. 2020-141380).

Disclosure of Invention

However, in the technique exemplified in patent document 1, it is not possible to provide an elastic wave device using a resonator having sound passband characteristics. The present invention provides an elastic wave device using a resonator which is more rectangular, has low loss, and has excellent passband characteristics.

An elastic wave device includes a piezoelectric substrate, and a band pass filter formed on the piezoelectric substrate and including a resonator having a first IDT electrode, a second IDT electrode, a third IDT electrode, a fourth IDT electrode, and a fifth IDT electrode, wherein the number of pairs of the third IDT electrode is greater than the sum of the number of pairs of the first IDT electrode, the number of pairs of the second IDT electrode, the number of pairs of the fourth IDT electrode, and the number of pairs of the fifth IDT electrode.

In one aspect of the present invention, the number of pairs of the first IDT electrodes is the same as the number of pairs of the fifth IDT electrodes.

In one aspect of the present invention, the number of pairs of the second IDT electrodes is the same as the number of pairs of the fourth IDT electrodes.

In one aspect of the present invention, the wiring pattern of the bandpass filter includes a first metal layer, a second metal layer formed on the first metal layer, and an insulator formed between the first metal layer and the second metal layer, the first metal layer includes an island-shaped pattern surrounded by and insulated from the signal line of the third IDT electrode, and the island-shaped pattern is electrically connected to the ground line of the second IDT electrode and the ground line of the fourth IDT electrode via the second metal layer.

In one aspect of the present invention, the piezoelectric substrate is bonded to a substrate on a principal surface opposite to a surface on which the band pass filter is formed, and the substrate is formed of one of sapphire, silicon, alumina, spinel, and glass.

In one aspect of the present invention, the band pass filter is a reception filter, and the elastic wave device is a duplexer further including a transmission filter.

In one aspect of the present invention, the passband frequency of the reception filter is lower than the passband frequency of the transmission filter.

In one aspect of the present invention, the transmission filter includes a plurality of resonators arranged in a ladder-type configuration.

In one aspect of the present invention, the plurality of resonators arranged in a ladder-type configuration of the transmission filter are acoustic thin film resonators.

In one aspect of the present invention, the transmission filter is formed on the piezoelectric substrate.

In one aspect of the present invention, a module including the elastic wave device is provided.

According to the present invention, it is possible to provide an elastic wave device using a resonator which is more rectangular, has low loss, and has excellent passband characteristics.

Drawings

Other features and effects of the present invention will become apparent from the following detailed description of the embodiments with reference to the accompanying drawings, in which:

fig. 1 is a cross-sectional view of an elastic wave device according to a first embodiment.

Fig. 2 is a schematic diagram of the structure of the device chip.

Fig. 3 is a schematic diagram showing resonance characteristics of the multimode resonator of the first embodiment and the comparative example.

Fig. 4 is a schematic diagram of the passband characteristics of the bandpass filters of the first embodiment and the comparative example.

Fig. 5 is a schematic structural view of an area surrounded by a dotted line in fig. 2.

Fig. 6 is a schematic diagram of the structure of the device chip.

Fig. 7 is a schematic plan view of the surface acoustic wave device as a surface acoustic wave resonator.

Fig. 8 is a schematic cross-sectional view of the elastic wave device being a piezoelectric thin film resonator.

Fig. 9 is a schematic diagram of the passband characteristics of the duplexer in the first embodiment.

Fig. 10 is a schematic structural diagram of a device chip in the second embodiment.

Fig. 11 is a cross-sectional view of a module of a third embodiment of the invention.

Detailed Description

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

(first embodiment)

Fig. 1 is a cross-sectional view of elastic wave device 1 according to a first embodiment.

As shown in fig. 1, elastic wave device 1 according to the first embodiment includes a wiring board 3 and two device chips 5 mounted on wiring board 3. Although the first embodiment exemplifies an elastic wave device in which one device chip 5(Rx) is used as a reception filter and the other device chip 5(Tx) is used as a transmission filter as a duplexer, the present invention is also applicable to an elastic wave device having a band pass filter of one device chip 5 or a duplexer. Further, a component that can realize the duplexer function can be formed on one device chip.

For example, a multilayer substrate made of resin or a Low Temperature Co-fired ceramic (LTCC) multilayer substrate formed of a plurality of dielectric layers may be used as the wiring substrate 3. The wiring board 3 includes a plurality of external connection terminals 31.

The device chip 5 is formed with a band pass filter through which an electric signal of a desired frequency band passes. A band pass filter including a multi-mode resonator is formed on the device chip 5 (Rx). In the first embodiment, the device chip 5(Rx) is a reception filter.

The device chip 5(Tx) has a ladder filter formed thereon. In the first embodiment, the device chip 5(Tx) is a transmission filter.

The device chip 5 may be formed of a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz, or a substrate made of piezoelectric ceramics. Alternatively, as described below, when the band pass filter uses an acoustic thin film resonator, a semiconductor substrate such as silicon or an insulating substrate such as sapphire, alumina, spinel, or glass may be used.

In addition, the device chip 5 may be a substrate in which a piezoelectric substrate and a supporting substrate are bonded to each other. For example, a sapphire substrate, an alumina substrate, a spinel substrate, or a silicon substrate can be used as the support substrate.

A plurality of electrode pads 9 are formed on the wiring substrate 3. The electrode pad 9 may be made of, for example, an alloy containing copper. Further, the thickness of the electrode pad 9 is, for example, 10 μm to 20 μm.

The encapsulating portion 17 is formed so as to cover the device chip 5. The sealing portion 17 may be formed of an insulator such as a synthetic resin, or may be formed of a metal. The synthetic resin may be, for example, an epoxy resin or polyimide, but is not limited thereto. Preferably, the sealing portion 17 may be formed by a low temperature hardening process using an epoxy resin.

The device chip 5 is mounted on the wiring substrate 3 by flip chip bonding (bumping) through bumps 15.

The bump 15 may be made of gold, for example. The height of the bump 15 is, for example, 20 μm to 50 μm.

The electrode pads 9 are electrically connected to the device chip 5 through the bumps 15.

Fig. 2 is a schematic diagram of the structure of the device chip 5 (Rx).

As shown in fig. 2, device chip 5(Rx) has a plurality of elastic wave elements 52 and a plurality of wiring patterns 54 formed thereon.

The elastic wave assembly 52 includes a multi-mode resonator 7. The multi-mode resonator 7 includes a first IDT electrode 71, a second IDT electrode 72, a third IDT electrode 73, a fourth IDT electrode 74, and a fifth IDT electrode 75.

In the first embodiment, the number of pairs of the first IDT electrodes 71 is 18. The number of pairs of the second IDT electrodes 72 is 22. The number of pairs of the third IDT electrode 73 was 96.5. The number of pairs of the fourth IDT electrode 74 is 22. The number of pairs of the fifth IDT electrodes 75 is 18. In other words, the number of pairs of the third IDT electrode 73 is greater than the sum of the number of pairs of the first IDT electrodes 71, the number of pairs of the second IDT electrodes 72, the number of pairs of the fourth IDT electrodes 74 and the number of pairs of the fifth IDT electrodes 75.

The number of pairs of the first IDT electrodes 71 is 18 as the number of pairs of the fifth IDT electrodes 75. The number of pairs of the second IDT electrode 72 and the fourth IDT electrode 74 is equal to 22.

The wiring pattern 54 has a first metal layer and a second metal layer (not shown in fig. 2), and an insulator (not shown in fig. 2) formed between the first metal layer and the second metal layer. The insulator may be polyimide, for example. The insulator is, for example, a thin film having a thickness of 1000 nm.

The wiring pattern 54 has a three-dimensional wiring portion 58, and the three-dimensional wiring portion 58 is wired so that the first metal layer and the second metal layer intersect each other three-dimensionally with the insulator interposed therebetween.

The acoustic wave device 52 and the wiring pattern 54 are formed of an appropriate metal or alloy such as silver, aluminum, copper, titanium, palladium, or the like. The metal patterns of the acoustic wave element 52 and the wiring pattern 54 may have a multilayer metal film structure in which a plurality of metal layers are laminated. The thicknesses of the elastic wave element 52 and the wiring pattern 54 are, for example, 150nm to 400 nm.

The wiring pattern 54 has wirings constituting an input pad In, an output pad Out, and a ground pad GND. The wiring pattern 54 is electrically connected to the acoustic wave device 52.

As shown in fig. 2, the third IDT electrode 73 is electrically connected to the output pad Out through the acoustic wave element 52 directly electrically connected to the output pad Out and through the three-dimensional wiring portion 58.

As shown in fig. 2, the band pass filter can be formed by disposing a plurality of elastic wave elements 52. The band pass filter is designed to pass only an electric signal corresponding to a desired frequency band among electric signals inputted from the input pad In.

An electric signal inputted from the input pad In passes through the band pass filter, and an electric signal In accordance with an intended frequency band is outputted from the output pad Out.

The electrical signal output from the output pad Out is output from the external connection terminal 31 of the wiring board 3 through the bump 15 and the electrode pad 9.

The waveform of the solid line indicates the resonance characteristics of the multi-mode resonator 7 of the elastic wave device of the first embodiment. The waveform of the broken line indicates the resonance characteristics of the multimode resonator of the comparative example. In the multi-mode resonator according to the comparative example, the number of pairs of the first IDT electrode is 18, the number of pairs of the second IDT electrode is 22, the number of pairs of the third IDT electrode is 78.5, the number of pairs of the fourth IDT electrode is 22, and the number of pairs of the fifth IDT electrode is 18. Other conditions are the same as those of the multi-mode resonator of the first embodiment.

As shown in fig. 3, although the first embodiment has the same pass band characteristics as the comparative example, the attenuation characteristics of the first embodiment are found to be preferable in the frequency range having a pass band higher than 820 MHz.

The waveform of the solid line indicates the pass characteristic of the band-pass filter of the elastic wave device in the first embodiment. The waveform of the broken line indicates the pass characteristic of the comparative example. The bandpass filter of the comparative example is a bandpass filter using a multimode resonator of the comparative example having resonance characteristics as shown in fig. 3. The other conditions are the same as those of the band-pass filter of the first embodiment.

As shown in fig. 4, the pass band characteristic, although the first embodiment has the same pass band characteristic as the comparative example, is found to be preferable in the attenuation characteristic of the first embodiment in the frequency range having a pass band higher than 820 MHz.

In other words, according to the present invention, it is possible to provide an elastic wave device using a multi-mode resonator which is more rectangular, has low loss, and has excellent passband characteristics.

Fig. 5 is a structural explanatory diagram of a region surrounded by a broken line in fig. 2.

As shown in fig. 5, the device chip 5(Rx) has a first metal layer 54M1 formed thereon. Further, the first metal layer 54M1 is formed with an island pattern IP surrounded by and insulated from the signal line L73 of the third IDT electrode 73.

The device chip 5(Rx) is further provided with a ground line GL of the second IDT electrode 72 and the fourth IDT electrode 74. Further, the device chip 5(Rx) is formed with a second metal layer 54M2 electrically connected to the ground line GL and the island pattern IP. An insulator 56 is provided between the second metal layer 54M2 and the signal line L73.

Thereby, the signal line L73, the insulator 56, and the second metal layer 54M2 constitute a three-dimensional wiring section 58 provided three-dimensionally.

The third IDT electrode 73 of the present invention has a problem that the insulator 56 is peeled off because of its large width. Therefore, the inventors have solved the problem of peeling of the insulator 56 by dividing the wiring connecting the third IDT electrode 73 and providing a plurality of three-dimensional wirings.

As shown in fig. 5, three solid wiring portions 58 may be formed after two island patterns IP are formed, or two solid wiring portions 58 may be formed after one island pattern IP is formed. In the case of forming one of the island-like patterns IP, the length thereof may be increased as needed.

Here, the three-dimensional wiring portion 58 has a parasitic capacitance formed between the signal line L73 and the second metal layer 54M2 of the ground line GL depending on the thickness and the area of the insulator 56, and may affect the characteristics of the band pass filter. The thicker the insulator 56, the smaller the parasitic capacitance, but the easier it is to peel off. The larger the area of the insulator 56, the less likely it is to be peeled off, but the parasitic capacitance increases.

Further, although the parasitic capacitance can be reduced by extending the length of the island pattern IP, the wiring pattern 54 of the signal line L73 is narrowed by extending the length excessively, and a problem of an increase in impedance value must be considered.

According to the structural design of the present invention, it is possible to perform optimum design while preventing characteristic deterioration due to peeling of the insulator 56 and parasitic capacitance. According to the structural design of the present invention, an elastic wave device having a high degree of freedom in design and excellent characteristics can be provided.

Fig. 6 is a schematic diagram of the structure of the device chip 5 (Tx).

As shown in fig. 6, the elastic wave module 52 and the wiring pattern 54 are formed on the device chip 5 (Tx).

The acoustic wave device 52 and the wiring pattern 54 may be formed of an appropriate metal or alloy such as silver, aluminum, copper, titanium, palladium, or the like. The metal patterns of the acoustic wave device 52 and the wiring pattern 54 may be, for example, a multilayer metal film in which a plurality of metal layers are laminated. The thicknesses of the elastic wave element 52 and the wiring pattern 54 are, for example, 150nm to 400 nm.

The wiring pattern 54 has wirings constituting the input pad In, the output pad Out, and the ground pad GND. The wiring pattern 54 is electrically connected to the acoustic wave device 52.

As shown in fig. 6, the band pass filter is configured by forming a plurality of elastic wave elements 52. The elastic wave device 52 has a plurality of resonators arranged in a ladder-type structure, which are series resonators and/or parallel resonators. The band pass filter is designed to pass only an electric signal corresponding to a desired frequency band among electric signals inputted from the input pad In.

Fig. 7 is a schematic plan view of the surface acoustic wave module 52 as a surface acoustic wave resonator.

As shown in fig. 7, the device chip 5 is provided with an idt (inter digital transducer)52a and a reflector 52b capable of exciting a surface acoustic wave. The IDT 52a has a pair of comb electrodes 52 c. The comb electrodes 52c are disposed to face each other. The comb electrode 52c has a plurality of electrode fingers 52d and a plurality of bus bars 52e connecting the electrode fingers 52 d. The reflectors 52b are disposed on both sides of the IDT 52 a.

The IDT 52a and the reflectors 52b are formed of an alloy of aluminum and copper, for example. The IDT 52a and the reflectors 52b are thin films having a thickness of 150nm to 400nm, for example. The IDT 52a and the reflectors 52b may be made of other metals, for example, suitable metals such as titanium, palladium, and silver, or alloys containing the above metals, or may be made of these alloys. The IDT 52a and the reflectors 52b may be a multilayer metal film structure in which a plurality of metal layers are laminated.

Fig. 8 is a schematic cross-sectional view of elastic wave module 52 being a piezoelectric thin film resonator.

As shown in fig. 8, a piezoelectric film 62 is provided on the chip substrate 60. The piezoelectric film 62 is sandwiched by a lower electrode 64 and an upper electrode 66. A gap 68 is formed between the lower electrode 64 and the chip substrate 60. The lower electrode 64 and the upper electrode 66 excite an elastic wave in a thickness longitudinal vibration mode in the piezoelectric film 62.

The chip substrate 60 is a semiconductor substrate such as silicon, or an insulating substrate such as sapphire, alumina, spinel, or glass may be used. The piezoelectric film 62 may be made of, for example, aluminum nitride. For example, a metal such as ruthenium may be used for the lower electrode 64 and the upper electrode 66.

The elastic wave module 52 can obtain desired characteristics of a band pass filter, and can be suitably applied to a multi-mode filter or a ladder filter.

Fig. 9 is a schematic diagram of the band characteristics of the duplexer in the first embodiment.

As shown in fig. 9, the frequency of the passband Rx of the reception filter of the duplexer in the first embodiment is lower than the frequency of the passband Tx of the transmission filter. In the duplexer having the frequency relationship as described above, the reception filter must be sharply suppressed on the high-frequency side of the pass band Rx thereof. In general, it is difficult to sharply suppress the high-frequency side of the passband of the multimode filter. However, according to the present invention, the duplexer having the above frequency relationship can obtain a passband characteristic in which both the passband of the reception filter and the passband of the transmission filter are good.

(second embodiment)

Fig. 10 is a schematic structural diagram of the device chip 105 in the second embodiment.

As shown in fig. 10, a reception filter RxBPF and a transmission filter TxBPF are formed on one device chip 105. Thereby, an elastic wave device as a duplexer can be provided on one device chip.

As shown in fig. 10, the input terminal in (rx) of the reception filter RxBPF is the same terminal as the output terminal out (tx) of the transmission filter TxBPF. The output terminal out (rx) of the reception filter RxBPF and the input terminal in (tx) of the transmission filter TxBPF may be disposed at positions farthest from each other on the device chip 105. The interference between the receive filter RxBPF and the transmit filter TxBPF can be reduced, and the characteristics of the duplexer can be improved.

In the design of the receive filter RxBPF and the transmit filter TxBPF on one device chip, the receive filter RxBPF may be a multimode filter in order to ensure that the receive filter RxBPF can suppress electric signals other than the passband in a space saving manner, and the transmit filter TxBPF may be a ladder filter in order to ensure power durability.

The other structures are the same as those of the first embodiment, and therefore, the description thereof is omitted.

(third embodiment)

Next, a third embodiment as another embodiment of the present invention will be described.

Fig. 11 is a cross-sectional view of a module 100 of a third embodiment of the present invention.

As shown in fig. 11, the elastic wave device 1 is provided on the main surface of the wiring board 130. For example, the duplexer described in the first or second embodiment may be used as elastic wave device 1. The wiring board 130 includes a plurality of external connection terminals 131. The external connection terminal 131 can be mounted to a main printed circuit board of a predetermined mobile communication terminal.

An inductor 111 is provided on the main surface of the wiring board 130 to achieve impedance matching. The inductor 111 may be an Integrated Passive Device (IPD). In the module 100, a plurality of electronic components including the acoustic wave device 1 are sealed by a sealing portion 117.

An integrated circuit component IC is provided inside the wiring board 130. The integrated circuit part IC includes a switching circuit and a low noise amplifier, which are not shown in the drawing.

The other structures are omitted because they overlap with the first and second embodiments.

According to the embodiments of the present invention described above, it is possible to provide an elastic wave device using a multi-mode resonator which is more rectangular, has low loss, and has excellent passband characteristics, and a module including the elastic wave device.

It should be noted that, of course, the present invention is not limited to the above-mentioned embodiments, and includes all embodiments capable of achieving the objects of the present invention.

Further, while at least one embodiment has been described above, it is to be understood that various changes, modifications, or improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the scope of the invention. It is to be understood that the aspects of the method or apparatus described herein are not limited in their application to the details of construction and the arrangements of the components set forth in the above description or illustrated in the drawings. The methods and apparatus may be practiced in other embodiments or with other embodiments. The examples are given by way of illustration only and not by way of limitation. Furthermore, the descriptions and words used herein are for the purpose of illustration only and are not intended to be limiting. The use of "including," "comprising," "having," "containing," and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of the term "or any term in the description of" or "can be construed to mean one, more than one, or all of the recited term(s). Any terms of front, back, left, right, top, bottom, up and down, and vertical and horizontal are used for convenience of description, and do not limit the position and spatial arrangement of any constituent element in the present invention. Accordingly, the foregoing description and drawings are by way of example only.

Claims

1. An elastic wave device comprising a piezoelectric substrate, and a band pass filter formed on the piezoelectric substrate and including a resonator having a first IDT electrode, a second IDT electrode, a third IDT electrode, a fourth IDT electrode, and a fifth IDT electrode, wherein the number of pairs of the third IDT electrode is greater than the sum of the number of pairs of the first IDT electrode, the number of pairs of the second IDT electrode, the number of pairs of the fourth IDT electrode, and the number of pairs of the fifth IDT electrode.

2. The elastic wave device according to claim 1, wherein: the number of pairs of the first IDT electrodes is the same as the number of pairs of the fifth IDT electrodes.

3. The elastic wave device according to claim 1, wherein: the number of pairs of the second IDT electrodes is the same as the number of pairs of the fourth IDT electrodes.

4. The elastic wave device according to claim 1, wherein: the wiring pattern of the band-pass filter includes a first metal layer, a second metal layer formed on the first metal layer, and an insulator formed between the first metal layer and the second metal layer, the first metal layer includes an island-shaped pattern surrounded by and insulated from the signal line of the third IDT electrode, and the island-shaped pattern is electrically connected to the ground line of the second IDT electrode and the ground line of the fourth IDT electrode via the second metal layer.

5. The elastic wave device according to claim 1, wherein: the piezoelectric substrate is bonded to a substrate on a main surface opposite to a surface on which the band pass filter is formed, and the substrate is formed of one of sapphire, silicon, alumina, spinel, and glass.

6. The elastic wave device according to claim 1, wherein: the band pass filter is a reception filter, and the elastic wave device is a duplexer further including a transmission filter.

7. The elastic wave device according to claim 6, wherein: the passband frequency of the receive rate filter is lower than the passband frequency of the transmit filter.

8. The elastic wave device according to claim 6, wherein: the transmission filter has a plurality of resonators arranged in a ladder-type structure.

9. The elastic wave device according to claim 8, wherein: the plurality of resonators arranged in a ladder-type configuration of the transmission filter are acoustic thin film resonators.

10. The elastic wave device according to claim 6, wherein: the transmission filter is formed on the piezoelectric substrate.

11. A module comprising the elastic wave device according to any one of claims 1 to 7.